Drivers:iio:adc:ti_am335x_adc remove comparison to bool

This is the patch to the file ti_am335x_adc.c
which fixes the following coccinelle warning:

WARNING: Comparison to bool

Signed-off-by: Venkat Prashanth B U <venkat.prashanth2498@gmail.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>